Hello, please forgive the cross-posting, this actually is quite important. I'll be brief.

If you don't know what bootstrapping is, I'm referring to the use of semantic HTML markup to configure advanced controls, which are then magically converted into dynamic interactive components when the content finishes loading.

Twitter Bootstrap is the most well-known CMS that does this.

The problem with the vast majority of interactive components used by Twitter Bootstrap and others, is that they are not specifically designed to be accessible from the start. The result is a negative impact across millions of pages across the web, as inaccessible components are repeatedly shared and incorporated into new projects daily.
E.G http://ux.joomla.org/forum/Accessibility/435-Bootstrap-and-Accessibility
or you can simply google "bootstrap accessibility" to find more examples. Though some work is being done in this regard, the majority of complex components are not accessible by WCAG2.0 or Section-508 standards as a result of this.